Plagger is like pipes for news feeds. You can read feeds from almost anywhere and output them to almost anywhere. It's written in perl.
xFruits is a sort of Yahoo! Pipes type service where you can take content and munge it into different forms. RSS to Atom, RSS to email, x RSS to 1 RSS, etc, etc.
I think Dapper turns any static site into dynamic content (RSS, XML, and more), widgets, facebook apps, etc. It's a content dynamifier I suppose.